Process of preparing fibers and yarns



Patented May 3, 1949 Ralph E. Montonna. and Hoyd H. Beyer-son,

Paul, and Elias Amdur, Minnea assignors to Regents of the Univ'e polls, .Minn., it! of Minnesota, Minneapolis, Minn, a corporation Minnesota 1 No Drawing. Application April 3, 1944, Serial No.- 529,425

This invention relates to methods of preparing and conditioning vegetable fibers for spinning and particularly to methods of treating unretted bast fibers of flax, hemp, ramie, and the like, plants. The invention may be applied to vegetable fibers obtained from immature plants such as flax which is pulled in the green stage, but particularly advantageous results are obtained when utilizing bast fibers from unretted mature vegetable fibers such as the bast fibers from dry, mature flax straw remaining after the threshing of flax seed. Vast quantities of such dry, mature flax straw are available from the flax seed industries, and there has heretofore been no substantial use for it.

It is an object of thei-nvention to provide new methods of preparing and conditioning vegetable fibers for spinning, and more particularly to provide methods of treating the best fibers from unretted or retted, mature or immature flax, hemp, ramie, and the like, vegetable plants in preparation for spinning such fibers. It is a further object of the invention to provide methods having particular merit in the treatment of the mature, dry flax straw remaining from the flax seed-growing industry.

To obtain the bast fiber starting material of the invention, the raw plant is first treated by conventional mechanical methods to remove the bast fibers from the shives of the plant. This mechanical treatment varies with the state of development of the plant, 1. e. whether it is mature or immature and also depends upon the particular plant material being processed. Thus, when the plant material is mature, unretted, dry flax straw, the straw is first passed through a flax breaker consisting of corrugated rollers. These serve to loosen the bast fibers from the shives and to effect a separation of a substantial portion of the shivey material. The resultant fibrous material, having some adhering shives thereon, is then further treated by passing the fibers through one or more combing or carding operations to separate adhering shive particles. The resultant bast fibers which constitute the starting material of this invention are then ready for processing to prepare the fibers for spinning.

In carrying out the invention the bast fiber starting material is, optionally, first washed using either plain hot water, a mild alkali, or a spent solution (from a later step of the process as herein described) containing originally .1% to 5% of sodium carbonate and.01% to.5% of hexametaphosphate or similar glassy metaphosphates. The washing step is optional, but we have dis- 7v Claims. (01. 57-464) 1 covered its use to be advantageous in that about 20% of non-fibrous material is-.thus loosened 1 and removed. The-washing, when used, is preferably followed by a cold water rinse oi the fibrous material.

To condition the '..fibers 3 for spinning, the (optionally .washed) hast fibers-are first treated with an aqueous oxidizing solution. As the oxidizing agent there is preferably used oxygencontaining acids of the-halogen series, or the salts or anhydrides of such acids,. such oxygen containing acids, salts and anhydrides being characterized by having an 5 oxidizing power equivalent to chlorous-acid, its-saltsand anhydrides. As the oxidizing agent there may also be used hydrogen peroxide or its derivatives, such as perboric acid and its salts, percarbonic acid and its salts and organic hydrogen .peroxide derivatives. Chlorous acid and its salts, particularly sodium or potassium chlorite have especially favorable reaction characteristics and such materials are preferred. i

Onepart by weightof oxidizing agent is sumcient to treat from 10 to 50 partsot bast fibers. The amount of water used in makingup the solution of oxidizing agent is preierably'the minimum amount needed for wetting Jr-covering the batch of fibers, usually from 100 to 5000 parts by weight of water for each part by 'weight'of oxidizing agent (or for each 10 to 50 parts by weight of bast fiber). For some opefationsthe amount of solution of oxidizing agent used is .simply enough to soak into the of, hast fibers, and after the requisite time period of reaction, hereinafter defined, it is rinsed. out and.,.the fiber treated in a subsequent step as hereinafter. described.

- We prefer, however, to use a suflicient volume of aqueous oxidizing agent solution to permit the working of the fibers in the solution, or conversely, the pumping of the solution repeatedly through the mass of best fibers. The latter method is advantageous-where a sllveror roving of the bast fiber is treated whilewound on a spool. Movement of the solution through the fibers not only makes for uniformity of treatment but also serves to some extent to f loosen and wash out the pectin-like cementitious materials that are softened by .the oxidizing agent solution. r

The temperature during the oxidative step ranges from room temperature to the boiling point of the solutions used. -WhIen chlorous acid. or its salts such assodiumchlorite are used as the oxidizing agent, .the 'preferred temperature range is from C. to boiling temperature of the solution, namely, about 100 C. when using hydrogen peroxide or its derivatives, as hereindefined, the preferred temperature range is from point of the solutions, namely, about 100 C. The solution of oxidizing agent is buffered to pH 3.5-11, a pH in the range of pH 3.5- being prei ferred when there is utilized as the oxidizing agent, an oxygen-containing acid of the halogen series or the salts or anhydrides of such acids, and a pH in the range of pH 7-11 is preferred when there is utilized hydrogen peroxide or its derivatives such as perboric acid and its salts, such as sodium perborate, percarbonic acid and its salts, or the organic hydrogen peroxide derivatives such as benzoyl peroxide.

Where sodium perborate is used a concentration of 1%-5%, based upon the amount of straw used, gives good results. Chlorine dioxide in stoichiometric amounts equivalent to the aforementioned range of sodium chlorite gives good results, as does also hydrogen peroxide, likewise in stoichiometric equivalent amounts and preferably stabilized with a small amount of sodium silicate.

Sodium hypochlorite is unsatisfactory as an ing potential, with the result that the pectin-like cementitious substances cementing the ultimate fibers together in the bast fibers, are removed or softened to an excessive degree and the resultant yarns lack tensile strength when dry. In addition sodium hypochlorite cannot be used at the higher temperatures under such conditions because the cellulose is oxidized and the fibers completely destroyed.

The treatment of the bast fibers with the solution of oxidizing agent is continued from 5 minutes to several hours, depending upon the amount of material treated and the facilities for movement of the oxidizing agent solution through the bast fibers or for working the fibers in the solution. The oxidizing agent solution is then drained or pumped from the so-treated bast fibers and the fibers are rinsed in plain .water.

The bast fibers are then treated with a weak alkaline solution, for example a weak solution of caustic alkali, such as sodium or potassium hydroxide or sodium or potassium carbonate. The alkaline solution is used in a concentration of .1% to 5%, 1% being preferred for most treatments. The treatment with alkaline solution is carriedout at elevated temperatures, preferably in the range from 50? C. to the boiling point of the caustic solution, which is approximately 100 C. Where the alkaline material chosen for treatment is sodium or-potassium carbonate, there is included in the alkaline solution an assisting agentsuch as sodium hexametaphosphate or similar glassy hexametaphosphates. For this purpose there may be used Calgon (registered trademark) which is principally a glassy sodium hexa-, metaphosphate. The assisting agent is included in the mild caustic alkali solution in a concentration of .01% to .5%, .1% being more effective and preferred. The spent solution of carbonate and assisting agent may, if desired, be used'for the (optional) initial washing step, as indicated pared bast fibers are then immediately spun while of intermediate drying and re-wetting of the' fibers. For this mode of operation the prelimiabout 20 C. (room temperature) to the boiling oxidizing agent because it has too high an oxidiz still in the wet condition so as to avoid the cost nary mechanical working of the fibers includes not only the breaking; and removing of shivey material but also the requisite mechanical steps necessary for producing a sliver or roving of bast fibers. Very satisfactoryresults are obtained by first making a sliver or roving of bast fibers, which are then wound on a perforated bobbin, either plainor cross-wound, and the full bobbin of roving is then handled as a unit through the (optional) washing, oxidizing and caustic treatment steps of the fiber preparation treatment. At the end of the caustic treatment, after the caustic has been rinsed from the bobbin of prepared roving or sliver, the bobbin is sent to suitable spinning machines which are arranged for wet spinning of the fibers.

It is to be understood, of course, that bast fibers spun whilewet, suitable draft being applied while spinning. We have discovered that the treatment of th bast fibers, as hereindescribed, whether the bast fibers are in the tow, sliver or roving stage, apparently produces a permanent change in the cementitious material binding together the ultimate fibers, with the result that an intermediate drying after the fiber treatment and before spinning is not detrimental, other jthan the expense involved. It is, however, more practical initially to work up the bast fibers into a strand such as a sliver or roving, of a size suitable for spinning, and then, while in this condition to treat the bastv fibers so as to condition them for spinning. In this way it is feasible to treat the fibers on bobbins The chemical mechanism of the fiber prepara- 1 tion is not completely understood, but is believed to be as follows: It is believed that the fiber preparation serves to soften. and possibly efiect complete removal of the pectin-like cementitiousma-' terial which serves in the plant stem to bind the bast fibers together, and at the same time to eifect a softening (but not a removal) of the apparently somewhat different pectin-like cementitious material which serves in the plant material to cement the ultimate fibers together in the bast fibers. There'is some evidence to support the belief thatthere are two related but different types of pectin-like cementitious materials in the plant. The softening and removal of the cementitious material which binds the bast fibers together permits the bast fibers to a large degree to separate from each other, and at the same time, the cementitious material which holds to-' gether the ultimate fibers in the individual bast fibers is softened to an extent suflicient to allow the ultimate fibers to slide relative to each other when drawn during spinning. The explanation of theory, given herein as an aid to understanding the invention, is not to be understood as a limitation thereon.

While the sliver or roving is in this moist prepared condition at the end of the flber preparation treatment, or if it has been allowed to dry, when re-wetted, the sliver or roving is passed through a wet spinning machine in which provision is made for drafting the sliver or roving while spinning. In such a machine the hast fibers are placed under tension by spaced pairs or rollers operating at increased speed and the bast fibers are drawn out as they are spun with the result that a distinct degree of slippage occurs between the ultimate flbers, and exceedingly fine yarns may be produced. Under advantageous conditions, it is possible when ultilizing the fiber preparation treatment of the present invention and wet spinning, as aforesaid, to produce from hard, dry, mature flax straw, fine linen yarns ranging in size from 30 lea to 150-175 lea.

The preparation treatment depends upon the use of an oxidation treatment wherein the oxidizing potential in respect to the material undergoing treatment is carefully selected and followed by a mild alkali treatment to cause a softening but not a removal of the pectin-like cementitlous material which binds together the ultimate fibers into bast fibers. This pectin-like material hardens in the spun yarn, yielding a strong yarn, capable of undergoing manufacturing treatment incident-to winding, twisting, weaving, etc.

A small amount of incidental bleaching occurs in the fiber preparation, the color being dependent upon the condition of the raw plant material (straw), its age and development. As a rule, linen yarns produced in accordance with the present invention from hard, dry, mature flax straw have a color ranging from ecru to about one-half white, depending upon the condition of the flax straw. Bleaching however is not at- Example I Mature, dry, flax straw of the type left over from the threshing of flax in the production of linseed was decorticated and the decorticated flax fiber was freed from shivey material using meth ods and machinery of the type commonly used for the preparation of roving from bast fibers.

The roving was wound on bobbins having a perforated centerpiece and shaped so as to allow fluids to be injected into and withdrawn through the roving materials on the bobbin. Approximately one pound of roving was wound on each bobbin, and the bobbin having the roving thereon was placed in a vessel provided with a pumping arrangement capable of being fastened to the centerof the bobbin so as to permit liquids to be forced through the roving on the bobbin and then withdrawn in reverse flow through the center of the bobbin. Wth the bobbin in place on the apparatus, the roving was washed for 5 minutes with plain water at 100 C., during which time the water was alternately forced outward and drawn inward through the roving on the bobbin by means of pressure and suction alternately applied through the centerpiece of the bobbin. The roving was then finally rinsed with plain. cool water.

An oxidizing solution was prepared using .05 pound (5%) of sodium chlorite (NaClOz) and 10 weight). The pH of the oxidizing solution was adjusted at the outset by the addition of .05 pound (5%) of acetic acid. The oxidizing solution was then pumped back and forth through the roving on the bobbin for 15 minutes during which time the temperature of the oxidizing solution was maintained at 95 C. The oxidizing solution was then drained and the roving on the bobbin was rinsed with plain, cold water.

For each pound (dry weight) of roving undergoing treatment there was prepared 10 pounds of sodium hydroxide solution (1%), and this was heated to 95 C., and pumped back and forth.

through the roving on the bobbin, the treatment being continued for one-half hour, and at the end of that period, the bobbin was drained and again washed with plain, cold water. While still wet, the bobbin containing the thus prepared roving of linen bast fibers was taken to spinning equipment, equipped for wet spinning and for drafting the roving during spinning. A linen yarn of 20-80 lea having a color corresponding to conventional ecru was prepared. The lea number of the yarn so prepared may be varied widely, depending upon the weight of the roving and the draft used during spinning.

Example II A roving of flax bast fibers was prepared and treated as in Example I, except that the caustic alkali solution consisted of 10 pounds of water containing 1% of sodium carbonate and .1% of sodium hexametaphosphate (Calgon). Any other similar glassy hexametaphosphate may be used. A fine linen yarn of 20-50 lea was produced.

Example III A roving offlaxbast fiber was treated as in Example I except that the preliminary washing was carried out using the spent alkali treatment of Example II. An exceptionally uniform linen yarn of high lea number (60 lea) wa produced.

Example IV- A roving of flax bast fibers was prepared and wound on the bobbin and washed with plain water as in Example I. It was then treated with an oxidizing solution composed of 10 pounds of water and 2 pounds of sodium perborate. The solution was maintained at a temperature .of C. and the oxidizing treatment was continued by pumping the solution back and forth through the roving on the bobbin for one-half hour, after which the oxidizing solution was drained and the roving rinsed with plain cold water. The roving was then treated with an alkaline solution composed of 10 pounds of water containing 1% sodium carbonate and .1% of sodium hexametaphosphate, as in Example III, the treatment being continued for one-half hour at C., after which the alkaline solution was drained, the roving rinsed with cold water and wet spun. A linen yarn of 20-30 lea having a color ranging from ecru to approximately the same as one-half white linen was produced.

While the chemical treatment of the present invention has particular merit for the treatment of flbers of mature plants, it may be pointed out that excellent results are also obtained when utilizing as the fibrous raw material the fibers of immature green flax Or retted flax or retted hemp,

in'which cases finer number yarns can be spun by preliminarily treating such fibers chemically as herein provided, than can be obtained when Pounds of Water for each pound of roving (dry 75 the ordinary retted roving is spun directly. Thus earn an ordinary retted flax roving capable of being spun' to, for example, 20 lea yarn, can be spun much finer by first chemically treating the fibers of the roving as herein provided.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that we do not limit ourselves to the specific embodiments herein except as defined by the appended claims.

What we claim is:

1. The process of preparing fine linen yarns from mature, dry flax straw which comprises decorticating the straw to free the best fibers from the shivey material and forming a roving of the bast fibers so separated, winding the roving on perforated bobbins, washing the roving with water for about five minutes at 100 C. by forcing the water through the roving on the bobbin, rinsing the roving in cool water and then draining it, then treating the roving with an oxidizing solution prepared by using .05 pound of sodium chlorite and .05 pound of acetic acid and 10 pounds of water for each pound of roving, dry weight, said oxidizing solution being pumped through the roving for about fifteen minutes while maintaining the temperature of the solution at about 95 0., rinsing the roving in plain cold water, treating the roving with about 10 pounds of approximately 1% sodium hydroxide solution by pumping the same through the roving for about one-half hour while maintaining the temperature at about 95 C.'and then after rinsing the roving in cold water and while the roving is still wet, drafting and spinning the roving into linen yarn. I

2. The process of preparing fine linen yarns from mature, dry flax straw which comprises decorticating the straw to free the bast .fibers from the shivey material and forming a roving of the bast fibers so separated, winding the roving on perforated bobbins, washing the roving with water for aboutfive minutes at 100 C. by forcing the water through the roving on the bobbin, rinsing the roving in cool water and then draining it, then treating the roving with an oxidizing solution prepared by using .05 pound of sodium chlorite and .05 pound of acetic acid and 10 pounds of water for each pound of roving, dry weight, said oxidizing solution being pumped through the roving for about fifteen minutes while maintaining the temperature of the solution at about 95 C., rinsing the roving in plain cold water, treating the roving with about 10 pounds of approximately 1% sodium hydroxide solution containing about .1% sodium hexametaphosphate by pumping the same through the roving for about one-half hour while maintaining the temperature at about 95 C. and then, after rinsing the roving in cold water and while the roving is still wet, drafting and spinning the roving into linen yarn.

3. The process of treating a roving of bast fibers of hard, dry, mature flax straw for spinning which comprises washing the roving for about five minutes at, about 100 C. with water, rinsing the roving in cold water, .treating the roving for about fifteen minutes at about 95 C. with about 10 pounds of water containing about .05 pound of sodium chlorite and adjusted to about pH 3.5 to 5.0 for each pound (dry basis) of roving present, rinsing the roving and then treating it with about a 1% solution of sodium hydroxide for about onehalf hour while maintaining the temperature at about 95 C. and then rinsing the roving preparatory to drafting and spinning while wet.

4. The process of treating a roving of best fibers of hard, dry, mature flax straw for spinning which comprises washing the roving for about five minutes at about 100 C. with water, rinsing the roving in cold water, treating the roving for about fifteen minutes at about 95 C. with about 10 pounds of water containing about .05 pound of sodium chlorite and adjusted to about pH 3.5 to

5.0 for each pound .(dry basis) of fibers present, I

rinsing the roving and then treating it with about a 1% solution of sodium hydroxide containing about .1% hexametaphosphate for about one-half hour while maintaining the temperature at about 95 C. and then rinsing the roving preparatory to drafting and spinning while wet.

5. The process of treating a roving of hard, dry, mature flax straw for spinning which comprises washing the roving, treating the roving for from five minutes to several hours at a'temperature of about 50 to 100 C. with one pound of a material selected from the class consisting of chlorous acid, its salt and anhydride in 100 to 5000 pounds of water adjusted to a pH of about pH 3.5 to 5.0 for each 10 to 50 pounds of roving (dry basis) present, rinsing the roving and then treating it with a .l% to 5% caustic solution for five minutes to several hours while maintaining the temperature at about 50 to 100 C. and then rinsing the roving preparatory to drafting and spinning while wet.

6. The process of treating a roving of hard, dry, mature flax straw for spinning which comprises washing the roving in a mild alkali solution, rinsing the roving in water, treating the roving for from five minutes to several hours at a temperature of about'50 to 100 C. with one pound of sodium chlorite in 100 to 5000 pounds of water adjusted to a pH .of about pH 3.5 to 5.0 for each 10 to 50 pounds of roving (dry basis) present, rinsing the roving and then treating it with a .l% to 5% caustic solution for five minutes to several hours while maintaining the temperature at about to 100 C. and then rinsing the roving preparatory to drafting and spinning while wet.

7. Theprocess of treating a roving of hard, dry, mature flax straw for spinning which comprises v washing the roving in a mild alkali solution, rinsing the roving in water, treating the roving for from five minutes to several hours at a temperature of about 50 to C. with one pound of sodium chlorite in 100 to 5000 pounds of water REFERENCES jcrrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re.'608 Ladd Oct. 5, 1858 487,875 Eves -1 Dec. 13, 1892 1,025,435 Weiberg May '7, 1912 1,053,125 1.'air Feb. 11, 1913 -(Other references on following page) Number Number 9 UNITED STATES PAI'EN'I'S Name Date Runkel Oct. 13, 1925 Hamberger Apr. 13, 1926 Clark 'June 8, 1926 Franz Oct. 7, 1930 Taylor- Jan. 17, 1933 Greene Oct. 6, 1936 Brandwood Sept. 21, 1937 Taylor Nov. 30, 1937 Eves Sept. 6, 1938 Vincent July 18, 1939' Korte Nov. 14, 1939 Pierce Feb. 4, 1941 Dubeau Aug. 9, 1941 MacMahon Aug. 19, 1941 Job Apr. 11, 1944 FOREIGN PATENTS Country Date Great Britain 190 Great Britain Apr. 10, 1922 Number .10 Country Date Great Britain Mar. 22, 1923 Great Britain Aug. 17, 1925 Great Britain Dec; 14, 1928 Great Britain Mar. 2, 1945 Germany Apr. 18, 1910 Germany Jan. 14, 1921 Germany June 2, 1921 Germany Jan. 11, 1924 Germany Dec. 16, 1924 Germany Nov. 14, 1930 France May 28, 1921 OTHER REFERENCES Chemical Abstracts, vol. 37, pages 1865-6. 15 Paper Industry and Paper World," July 1943,

page 444.

(1942), pages 326-7.

Certificate of Correction Patent No. 2,468,771 May 3, 1949 RALPH E. MONTONNA ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 7, line 72, for the word roving read fibers;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 7th day of February, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

